The present disclosure is directed to new compositions, such as fuser fluids, fuser oils or release agents, selected for use during the fusing of electrostatic toner particles. The compositions possess a number of advantages, such as enhancing the release of toner particles, particularly polyester and styrene butadiene based toner particles, from a fuser roll or similar components in various apparatuses such as an electrostatic, especially xerographic, reproducing apparatuses. More particularly, the present disclosure is directed to a mixture of, such as a solution of, mercapto-functional polyorganosiloxanes and amino-functional polyorganosiloxanes, and to fuser members (hard or soft) coated or impregnated therewith, that can exhibit in various embodiments advantages such as enhanced release and extended fuser life and improved paper interactions. A further development disclosed herein is directed to a fuser member comprising a substrate, a polymeric layer thereover, preferably comprising a fluoropolymer or fluoroelastomer, and, on the layer, a coating of an organosiloxane polymer release agent comprising specific amounts of mercapto- and amino-functionalities.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which can be the photosensitive member itself, or some other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Through the use of heat and pressure over a given amount of time, the material becomes fixed. Thereafter, as the toner material cools, solidification of the toner material causes the toner to be bonded firmly to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of from about 90° C. to about 200° C. or higher, depending on the softening range of the particular resin used in the toner. It may be undesirable, however, to increase the temperature of the substrate substantially higher than about 250° C. because of the tendency of the substrate to discolor or convert into fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat can be applied by heating one or both of the rolls, plate members, or belt members. Fusing of the toner particles occurs when the proper combination of heat, pressure, and/or contact for the optimum time period are provided. The balancing of these variables to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
During the operation of one fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between a pair of rolls, plates, belts, or combination thereof. The concurrent transfer of heat and the application of pressure in the nip effects the fusing of the toner image onto the support. It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member can subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thereby increasing the image background, causing inadequate copy quality, causing inferior marks on the copy, or otherwise interfering with the material being copied there as well as causing toner contamination of other parts of the machine. The referred to “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release properties of the fuser member, and accordingly it is desirable to provide a fusing surface having a low surface energy to provide the necessary release.
To ensure and maintain good release properties of the fuser member, it has become customary to apply release agents to the fuser member during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils, such as polydimethyl siloxane (PDMS), or substituted silicone oils, such as amino-substituted oils, mercapto-substituted oils, or the like, to prevent toner offset. In addition, fillers can be added to the outer layers of fuser members to increase the bonding of the fuser oil to the surface of the fuser member, thereby imparting improved release properties.
The use of polymeric release agents having functional groups which interact with a fuser member to form a thermally stable, renewable self-cleaning layer having good release properties for electroscopic thermoplastic resin toners, is described in, for example, U.S. Pat. Nos. 4,029,827, 4,101,686, and 4,185,140, the disclosures of each of which are totally incorporated herein by reference. Disclosed in U.S. Pat. No. 4,029,827 is the use of polyorganosiloxanes having mercapto-functionality as release agents. U.S. Pat. Nos. 4,101,686 and 4,185,140 are directed to polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether, and mercapto groups as release fluids.
It is of value to select the correct combination of fuser surface material, any filler incorporated or contained therein, and fuser oil. Specifically, it is important that the outer layer of the fuser member react sufficiently with the selected fuser oil to obtain sufficient release. As briefly mentioned above, in order to improve the bonding of fuser oils with the outer surface of the fuser member, fillers have been incorporated into or added to the outer surface layer of the fuser members. The use of a filler can aid in decreasing the amount of fusing oil necessary by promoting sufficient bonding of the fuser oil to the outer surface layer of the fusing member. It is important, however, that the filler not degrade the physical properties of the outer layer of the fuser member, and it is also important that the filler not cause too much of an increase in the surface energy of the outer layer.
Fillers are also sometimes added to the outer layers of fuser members to increase the thermal conductivity thereof. Examples of such fillers include conductive carbon, carbon black, graphite, titanium, boron nitride, zinc oxide, aluminum oxide, and the like, as well as mixtures thereof. Efforts have been made to decrease the use of energy by providing a fuser member that has excellent thermal conductivity, thereby reducing the temperature needed to promote fusion of toner to paper. This increase in thermal conductivity also allows for increased speed of the fusing process by reducing the amount of time needed to heat the fuser member sufficiently to promote fusing. Efforts have also been made to increase the toughness of the fuser member layers to increase abrasion resistance and, accordingly, the life of the fuser member.
With regard to known fuser coatings, hydrofluoroelastomers, Teflons® and silicone rubbers are traditionally used. For these coatings, release agents are required. Silicone rubbers interact well with various types of fuser release agents. Perfluoroalkoxypolytetrafluoroethylene (PFA Teflon), however, which is frequently used as an outer coating for fuser members, is more durable and abrasion resistant than silicone rubber coatings. Also, the surface energy for PFA Teflon is lower than that of silicone rubber coatings. Fluorohydroelastomers have relatively higher surface energy, are durable, and provide adequate release capability with the functionalized polydimethylsiloxane based release fluids.
U.S. Pat. No. 3,002,927 (Awe et al.), the disclosure of which is totally incorporated herein by reference, discloses organosilicon fluids capable of withstanding high temperatures which are prepared by preoxygenating the fluid by heating a mixture of (1) a polysiloxane fluid in which the siloxane units are selected from the group consisting of units of the formula R3SiO0.5, R2SiO, RSiO1.5, and SiO2 in which each R is selected from the group consisting of methyl, phenyl, chlorophenyl, fluorophenyl, and bromophenyl radicals, (2) a ferric salt of a carboxylic acid having from 4 to 18 carbon atoms in an amount such that there is from 0.005 to 0.03 percent by weight iron based on the weight of (1), and (3) oxygen mechanically dispersed in the fluid at a temperature above 400° F. until the mixture changes to a reddish brown color and until the mixture will not form a precipitate when heated in the absence of oxygen at a temperature above that at which the preoxygenation step is carried out.
U.S. Pat. No. 3,731,358 (Artl), the disclosure of which is totally incorporated herein by reference, discloses a silicone rubber roll for pressure fusing of electrostatically produced and toned images at elevated temperatures. The roll inherently prevents offset of the image by supplying a release material to the surface of the roll. When the release material is depleted, the roll can be restored by impregnation with silicone oil.
U.S. Pat. No. 4,011,362 (Stewart), the disclosure of which is totally incorporated herein by reference, discloses metal substrates such as molds and fuser rolls, which are coated with carboxyfunctional siloxanes to improve their release characteristics.
U.S. Pat. No. 4,029,827 (Imperial et al.), the disclosure of which is totally incorporated herein by reference, discloses polyorganosiloxanes having functional mercapto groups which are applied to a heated fuser member in an electrostatic reproducing apparatus to form thereon a thermally stable, renewable, self-cleaning layer having superior toner release properties for electroscopic thermoplastic resin toners. The polyorganosiloxane fluids having functional mercapto groups interact with the fuser member in such a manner as to form an interfacial barrier at the surface of the fuser member while leaving an unreacted, low surface energy release fluid as an outer layer or film. The interfacial barrier is strongly attached to the fuser member surface and prevents toner material from contacting the outer surface of the fuser member. The material on the surface of the fuser member is of minimal thickness and thereby represents a minimal thermal barrier. The polyorganosiloxanes having mercapto-functionality have also been effectively demonstrated as excellent release agents for the reactive types of toners having functional groups thereon.
U.S. Pat. No. 4,046,795 (Martin), the disclosure of which is totally incorporated herein by reference, discloses a process for preparing thiofunctional polysiloxane polymers which comprises reacting a disiloxane and/or a hydroxy or hydrocarbonoxy containing silane or siloxane with a cyclic trisiloxane in the presence of an acid catalyst wherein at least one of the organosilicon compounds contain a thiol group. These thiofunctional polysiloxane polymers are useful as metal protectants and as release agents, especially on metal substrates.
U.S. Pat. No. 4,101,686 (Strella et al.), the disclosure of which is totally incorporated herein by reference, discloses polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether, or mercapto groups. The release agents are applied to a heated fuser member in an electrostatic reproducing apparatus to form thereon a thermally stable, renewable, self-cleaning layer having excellent toner release properties for conventional electroscopic thermoplastic resin toners. The functional polymeric fluids interact with the fuser member in such a manner as to form a thin, thermally stable interfacial barrier at the surface of the fuser member while leaving an outer film or layer of unreacted release fluid. The interfacial barrier is strongly attached to the fuser member surface and prevents electroscopic thermoplastic resin toner material from contacting the outer surface of the fuser member. The material on the surface of the fuser member is of minimal thickness and thereby represents a minimal thermal barrier.
U.S. Pat. No. 4,146,659 (Swift et al.), the disclosure of which is totally incorporated herein by reference, discloses fuser members having surfaces of gold and the platinum group metals and alloys thereof for fuser assemblies in office copier machines. Preferred fuser assemblies include cylindrical rolls having at least an outer surface of gold, a platinum group metal, or alloys thereof. Electroscopic thermoplastic resin toner images are fused to a substrate by using a bare gold, a platinum group metal, or alloys thereof fuser member coated with polymeric release agents having reactive functional groups, such as a mercapto-functional polysiloxane release fluid.
U.S. Pat. No. 4,150,181 (Smith), the disclosure of which is totally incorporated herein by reference, discloses a contact fuser assembly and method for preventing toner offset on a heated fuser member in an electrostatic reproducing apparatus which includes a base member coated with a solid, abrasion resistant material such as polyimide, poly(amide-imides), poly(imide-esters), polysulfones, and aromatic polyamides. The fuser member is coated with a thin layer of polysiloxane fluid containing low molecular weight fluorocarbon. Toner offset on the heated fuser member is prevented by applying the polysiloxane fluid containing fluorocarbon to the solid, abrasion resistant surface of the fuser member.
U.S. Pat. No. 4,185,140 (Strella et al.), the disclosure of which is totally incorporated herein by reference, discloses polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether, or mercapto groups which are applied to a heated fuser member in an electrostatic reproducing apparatus to form thereon a thermally stable, renewable, self-cleaning layer having excellent toner release properties for conventional electroscopic thermoplastic resin toners. The functional polymeric fluids interact with the fuser member in such a manner as to form a thin, thermally stable interfacial barrier at the surface of the fuser member while leaving an outer film or layer of unreacted release fluid. The interfacial barrier is strongly attached to the fuser member surface and prevents electroscopic thermoplastic resin toner material from contacting the outer surface of the fuser member. The material on the surface of the fuser member is of minimal thickness and thereby represents a minimal thermal barrier.
U.S. Pat. No. 4,515,884 (Field et al.), the disclosure of which is totally incorporated herein by reference, discloses the fusing of toner images to a substrate, such as paper, with a heated fusing member having a silicone elastomer fusing surface by coating the elastomer fusing surface with a toner release agent which includes an unblended polydimethyl siloxane having a kinematic viscosity of from about 7,000 to about 20,000 centistokes. In a preferred embodiment the polydimethyl siloxane oil has a kinematic viscosity of from about 10,000 to about 16,000 centistokes and the fuser member is a fuser roll having a thin layer of a crosslinked product of a mixture of α,ω-dihydroxypolydimethyl siloxane, finely divided tabular alumina, and finely divided iron oxide.
U.S. Pat. No. 5,157,445 (Shoji et al.), the disclosure of which is totally incorporated herein by reference, discloses a fixing device where a copying medium carrying a nonfixed toner image thereon is passed between a pair of fixing rolls as being kept in direct contact with each other under pressure so as to fix the nonfixed toner image on the copying medium, the device being characterized in that a toner release at least containing, as an active ingredient, an amino-functional-group-containing organopolysiloxane of the general formula
the organopolysiloxane having a viscosity of from 10 to 100,000 cs at 25° C., is supplied to at least the fixing roll of being brought into contact with the nonfixed toner image of the pair of fixing rolls.
U.S. Pat. No. 5,395,725 (Bluett et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for fusing toner images to a substrate which comprises providing a fusing member having a fusing surface; heating the fuser member to an elevated temperature to fuse toner to the substrate; and applying directly to the fusing surface a fuser release agent oil blend composition; wherein volatile emissions arising from the fuser release agent oil blend are minimized or eliminated. The fuser release agent oil comprises the addition of small amounts of mercapto-functional polyorganosiloxanes to other functional fluids, including amino-functional polyorganosiloxanes, in order to enhance stabilization against degradation leading to volatile emissions.
U.S. Pat. No. 5,401,570 (Heeks et al.), the disclosure of which is totally incorporated herein by reference, discloses a fuser member comprising a substrate and thereover a silicone rubber containing a filler component therein, wherein the filler component is reacted with a silicone hydride release oil.
U.S. Pat. No. 5,493,376 (Heeks), the disclosure of which is totally incorporated herein by reference, discloses a thermally stabilized polyorganosiloxane oil including a polyorganosiloxane oil and, as the thermal stabilizer, the reaction product of chloroplatinic acid and a member selected from the group consisting of a cyclic polyorganosiloxane having the formula
where R3 is an alkyl radical having 1 to 6 carbon atoms and R4 is selected from the group consisting of alkene and alkyne radicals having 2 to 8 carbon atoms, and n is from 3 to 6; a linear polyorganosiloxane having the formula
wherein R1 and R2 are selected from the group consisting of hydroxy and alkyl, alkoxy, alkene, and alkyne radicals having 1 to 10 carbon atoms, provided that at least one of R1 and R2 is alkene or alkyne, and m is from 0 to 50; and mixtures thereof, present in an amount to provide at least 5 parts per million of platinum in said oil.
U.S. Pat. No. 5,512,409 (Henry et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of fusing thermoplastic resin toner images to a substrate in a fuser including a heated thermally stable FKM hydrofluoroelastomer fusing surface at elevated temperature prepared in the absence of anchoring sites for a release agent of heavy metals, heavy metal oxides, or other heavy metal compounds forming a film of a fluid release agent on the elastomer surface of an amino-functional oil having the formula
U.S. Pat. No. 5,516,361 (Chow et al.), the disclosure of which is totally incorporated herein by reference, discloses a fusing system, a method of fusing, and a fuser member having a thermally stable FKM hydrofluoroelastomer surface for fusing thermoplastic resin toners to a substrate in an electrostatographic printing apparatus, said fuser member having a polyorgano T-type amino-functional oil release agent. The oil has predominantly monoamino-functionality per active molecule to interact with the hydrofluoroelastomer surface to provide a substantially uniform interfacial barrier layer to the toner and a low surface energy film to release the toner from the surface.
U.S. Pat. No. 5,531,813 (Henry et al.), the disclosure of which is totally incorporated herein by reference, discloses a polyorgano amino-functional oil release agent having at least 85 percent monoamino-functionality per active molecule to interact with the thermally stable FKM hydrofluoroelastomer surface of a fuser member of an electrostatographic apparatus to provide an interfacial barrier layer to the toner and a low surface energy film to release the toner from the surface.
where 50<n<200, p is 1 to 5, RR2, and R3 are alkyl or arylalkyl radicals having 1 to 18 carbon atoms, R4 is an alkyl or arylalkyl radical having 1 to 18 carbon atoms and a polyorganosiloxane chain having 1 to 100 diorganosiloxy repeat units, and R5 is a hydrogen, alkyl, or arylalkyl radical having 1 to 18 carbon atoms, the oil having sufficient amino-functionality per active molecule to interact with the hydrofluoroelastomer surface in the absence of a heavy metal and heavy metal anchoring sites to provide an interfacial barrier layer to the toner and a low surface energy film to release the toner from the surface. The process entails contacting the toner image on the substrate with the filmed heated elastomer surface to fuse the toner image to the substrate and permitting the toner to cool.
U.S. Pat. No. 5,747,212 (Kaplan et al.), the disclosure of which is totally incorporated herein by reference, discloses a method of fusing and a fusing system for a fusing member having a thermally stable FKM hydrofluoroelastomer surface for fusing thermoplastic resin toners which are susceptible to amines to a substrate in an electrostatographic printing apparatus with an amino-functional oil having the formula:
where 50<n<200, p is 1 to 5, and R1, R2, and R3 are selected from the group consisting of alkyl and arylalkyl radicals having 1 to 18 carbon atoms, R4 is selected from the group consisting of alkyl and arylalkyl radicals having 1 to 18 carbon atoms and a polyorganosiloxane chain having 1 to 100 diorganosiloxy repeat units, and R5 is selected from the group consisting of hydrogen, alkyl and arylalkyl radicals having 1 to 18 carbon atoms, wherein at least 85 percent of the polyorgano amino-functional siloxane chains have p equal to 1 and the
groups are situated at random along the chain, said oil having predominantly monoamino-functionality per active molecule to interact with said hydrofluoroelastomer surface to provide an interfacial barrier layer to said toner and a low surface energy film to release said toner from said surface.
U.S. Pat. No. 5,864,740 (Heeks et al.), the disclosure of which is totally incorporated herein by reference, discloses a thermally stabilized silicone liquid composition and a toner fusing system using the thermally stabilized silicone liquid as a release agent, wherein the thermally stabilized silicone liquid contains a silicone liquid and a thermal stabilizer composition (including a reaction product from at least a polyorganosiloxane and a platinum metal compound (Group VIII compound) such as a ruthenium compound, excluding platinum.
U.S. Pat. No. 6,183,929 (Chow et al.), the disclosure of which is totally incorporated herein by reference, relates to a release agent comprising a mixture of a non-functional organosiloxane polymer with a functional organosiloxane polymer such as an amino-substituted or mercapto-substituted organosiloxane.
U.S. Pat. No. 6,253,055 (Badesha et al.), the disclosure of which is totally incorporated herein by reference, discloses fuser members coated with hydride release oils, and materials and imaging apparatus thereof.
U.S. Pat. No. 6,261,688 (Kaplan et al.), the disclosure of which is totally incorporated herein by reference, discloses tertiary amino-functionalized fuser fluids. The fuser fluids comprise polyorganosiloxanes having tertiary amino-functional groups on at least some of the molecules thereof.
With regard to known fusing oils, silicone oil has been the preferred release agent for coatings for fuser members. However, as noted above, many difficulties exist with the use of different types of silicone oils. As a result, while there are many different types of silicone oils, with a wide range of properties that vary according to the type of functional agent, molecular weight, viscosities, etc., a great deal of research continues in order to develop improved fusing oils or mixtures thereof.
Mercapto-functional polyorganosiloxane release fluids have frequently been utilized with the outer layers of fluoropolymer fuser members. These outer layers, or overcoats, of the fluoropolymer fuser members (or rolls) generally contain a metal oxide filler such as copper oxide or aluminum oxide. An example of such a fluoropolymer fuser roll is a copper oxide filled VITON® overcoat fuser roll. The mercapto groups present in the mercapto-functional polyorganosiloxanes bind to the copper oxide (CuO) sites to provide a fluid layer that protects the fuser member from toner contact. Such a combination has been successful (i.e., exhibits long release life) for producing black and white copies (black toner) utilizing styrene-butadiene based toner resins.
However, a much shorter release life has been observed when the mercapto-functional polyorganosiloxanes are utilized in the production of color prints. This is believed to be due to a number of factors, including the use of more highly reactive polyester toner resins, high levels of toner additives, higher toner pile heights, wider use of halftones and a larger area of coverage. Consequently, it would be beneficial to produce a fuser fluid, fuser oil or release agent that exhibits longer release life for use in printers capable of black and/or color printing, including classical black and white (I), full-color color image on image (IOI) and highlight color image next to image (INI) applications.
In this regard, amino-functional polyorganosiloxanes have been utilized for color printing. The amino groups do not require copper oxide anchor sites, as do the mercapto groups, because the amino groups can directly react with the fuser roll VITON® overcoat polymer itself. Accordingly, copper oxide filled VITON® overcoat fuser rolls are not necessary for color printing utilizing amino-functional polyorganosiloxanes.
Moreover, it has also been observed that because the amino groups in the amino-functional polyorganosiloxanes bind more firmly to the fuser roll surface than the mercapto groups, more robust protection can be achieved using the amino-functional polyorganosiloxanes than the mercapto-functional polyorganosiloxanes. The consequence of this mechanism is significantly longer fuser release life with amino-functional polyorganosiloxanes versus mercapto-functional polyorganosiloxanes.
However, when utilized for black and white printing (black toner), it has been found that high mole % amino-functional polyorganosiloxanes contaminate the paper path rolls, reducing their friction and causing slippage. This occurs due to the chemical interacting of the amino-functionality of the oil with the components of the paper. Additionally, the highly reactive amino groups sometime produce fuser roll contamination. Moreover, the amino-functional groups also produce side effects, which include post-processing difficulty with the writing, or typing, on the prints, difficulty with laminating, and poorer reliability due to the amino oil effect on the paper handling system.
Furthermore, it has also been noted that when mercapto-functional polyorganosiloxanes are utilized for black and white printing (black toner), additional fuser performance issues have occurred, depending upon toner composition. These include paper jams, shortened release life and image quality problems with high area coverage. Hence, it would be desirable to develop a fuser fluid, oil and/or release agent that can be utilized for black, highlighted color and full color utilizing IOI or INI, which overcomes the deficiencies noted above.
Moreover, a need remains for fuser release agents that do not interact chemically with copy substrates such as paper. Further, a need remains for fuser release agents that enable the production of prints upon which adhesives such as those on 3M Post-It® notes adhere adequately.
Additionally, a need remains for fuser release agents that enable the use of pre-printed forms. There is also a need for fuser release agents that enable the production of prints which can then be bound well with binder adhesives. In addition, there is a need for fuser release agents that react well with fluoropolymers and fluoroelastomers commonly used as fuser member outer layers. Further, there is a need for fuser release agents that form complete and uniform layers on fuser members having fluoropolymer surfaces. Moreover, there is a need for fuser release agents that enable long release life times for fuser members employed therewith. A need also remains for fuser release agents that protect the underlying fuser member materials from reactive toner materials, such as highly reactive polyester toner resins. In addition, a need remains for fuser release agents that prevent or reduce offset of paper and toner additives onto the fuser member.